Furnaces for treating ceramics



Aiag. 26, 1969 w. GREEN ET AL 3,463,470

FURNACES FOR TREATING CERAMICS Filed Dec. 28. 1967 FIG./

INVPINIORS WILLIAM GREEN JERZY RIAZANOW United States Patent O 3,463,470 FURNACES FOR TREATING CERAMICS William Green, New York, and Jerzy Riazanow, Yonkers, N.Y., assignors to Ceramivac Mfg. Inc., New York, N. a corporation of New York Filed Dec. 28, 1967, Ser. No. 698,089 Int. Cl. F27]: 5/10 US. Cl. 263-40 9 Claims ABSTRACT OF THE DISCLOSURE A furnace for treating ceramic materials. The furnace has a stationary support means which carries the work. A mufiie means defines a heating chamber in which the work is treated, and a moving means is operatively connected with the muflle means to displace the latter from a rest position where it is situated beyond the support means and the work carried thereby to an operating position where it encloses the work and at least part of the support means in the heating chamber so as to heat the work therein. As a result of this construction, the work remains absolutely stationary so that all possible vibrations are avoided and any tendency for the work to crumble during treatment thereof or during displacement of the heating chamber into its operative location enclosing the work is reliably prevented.

BACKGROUND OF THE INVENTION The present invention relates to furnaces.

In particular, this invention relates to furnace for treating ceramic materials such as porcelain and the like. Furnaces of this general type are used, for example, in dental laboratories by dental technicians for the purpose of manufacturing dental components.

As is well known, work material of this type is extremely delicate and great care must be taken not only during the actual treatment of the work by heating thereof but also during the transition period when the work becomes situated within a heating chamber of a furnace. Quite often, even with the exercise of considerable care, the removal of the moisture from the work results in crumbling thereof.

This latter highly undesirable property is extremely difficult to avoid because the work is subject to some degree of vibration during movement of the work into the heating chamber defined by the muffle of the furnace.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a furnace of the above general type which will avoid the above drawbacks.

In particular, it is an object of the invention to provide a furnace which will reliably avoid transmission of any vibrations to the work so that the latter will be very greatly protected against the possibility of crumbling or any other type of cracking or failure due to vibratroy movements which are transmitted to the work itself.

It is also an object of the invention to provide a relatively simple compact structure which can be very reliably operated without the exercise of great skill while at the same time achieving a vibration-free mounting of the work not only during the actual heating thereof in the furnace but also during transition of the work between its condition at the exterior of the furnace and its condition during the heating in the interior of the furnace.

It is particularly an object of the present invention to provide a furnace of the above type which is especially adaptable for use in dental laboratories in connection with the manufacture of dental components.

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In accordance with the invention, a support means is provided to carry the work, and this support means is stationary so that the work also is stationary. A muffie means which defines a heating chamber of the furnace in which the work is to be treated is supported for movement with respect to the support means and the work which is carried thereby, and a moving means is operatively connected to the mufile means to displace it between a rest position situated beyond the support means and the work carried thereby and an operating position where the heating chamber of the mufile means encloses the work and at least part of the support means which carries the work.

BRIEF DESCRIPTION OF DRAWINGS The invention as illustrated by Way of example in the accompanying drawings which form part of this application in which:

FIG. 1 is a perspective illustration of one possible embodiment of a structure of the invention.

FIG. 2 is a fragmentary sectional elevation taken along line 2-2 of FIG. 1, in the direction of the arrows and showing the details of the furnace structure at an enlarged scale, as compared to FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings, the furnace 10 which is shown therein for treating a ceramic material, such as a work piece 12, includes a support means 14 which is stationary and carries the work 12 so that the work 12 also will remain stationary when mounted on the support means 14. This support means includes a simple pedestal 16 having an upper cylindrical end provided with a top surface on which the work 12 rests. The lower end of the pedestal 16 has an enlarged diameter and may be provided with a gasket 18 in the form of a silicone pad ring resting on a lower portion 20 of the support means and surrounding a portion 22 thereof which is of a diameter between the diameter of the upper part of the pedestal 16 and the base part 20 thereof which carries the gasket 18. The support means further includes a base plate 24 which fixedly carries the pedestal 16 in any suitable way.

This base plate 24 forms the top wall of an instrument housing 26 which contains and carries the instruments and controls for the furnace. Thus, the front wall 28 of the housing 26 carries, for example, a vacuum gauge 30, a relief valve control 32, a switch 34 for actuating a chamber lift, as described below, a meter setting control 36, a timer 38, a current adjuster 40, a main switch 42, a buzz switch 44, an ammeter 46, an indicating light 48, and a fuse 50.

The chamber lift switch 34 is provided to actuate a moving means which is capable of displacing a muffle means with respect to the support means 14. The mufiie means 52 is of a generally cylindrical configuration and has a rest or inoperative position shown in FIG. 1, where it is displaced above the support means 14, so that at this time the work 12 can be placed on or removed from the top surface of the support means 14.

The rnufile means 52 has the outer metallic, cylindrical housing 54 in which is located a ceramic mufile 56 defining a heating chamber 58 which has an open bottom, this chamber 58 itself being of a cylindrical configuration. The cylindrical wall 54 is closed by a top plate 60 which has at its lower peripheral surface a ring 62 for properly locating the plate 60 on the cylinder 54, and suitable screws 64 may be provided for fixing the closure plate 60 to the cylindrical housing 54 of the muffle means so as to enclose the ceramic muflle member 56 within the housing. At its lower end the housing 54 has an inwardly directed circular flange 66 whose inner periphery is of a diameter precisely matching the exterior diameter of the portion 22 of the support means.

In order to heat the muffle means 54, a source of energy is connected thereto by way of a thermocouple and power connecting assembly 68 connected to the wiring 70 which heats the muffle, as shown schematically in FIG. 2, and a flexible, electrically conductive connecting structure 72 serves to connect the thermocouple and power connecting structure 68 to a source of energy.

When the muflle means 52 is in its lower operative position shown in FIG. 2, the part of the pedestal 16 which is above the portion 22 thereof is received in the interior of the chamber 58, and the opening defined by the lower flange 66 is completely closed by the portion 22 of the support means. A vacuum tube 74 extends through the support means to communicate with the interior of the chamber 58 when the mufile means 52 is in its lower operative position shown in FIG. 2, and this vacuum tube 74 is connected with any suitable source of vacuum so that the interior of the heating chamber 58 can be evacuated. The relief valve control 32 is actuated at the end of the operation in order to raise the pressure in the chamber 58 so that thereafter the muffle means can be returned upwardly to its rest or inoperative position shown in FIG. 1.

In accordance with the present invention not only is the support means 14 stationary and the muffle means 52 movable so that the heating chamber 58 is displaced with respect to the work, rather than work with respect to the heating chamber, but in addition a moving means 76, actuated by the chamber lift switch 34, is provided for displacing the muflle means 52 in a smooth, vibrationfree manner.

For this purpose the muflle means is fixedly connected with a plurality of rods 78 of the moving means. In the illustrated example, there are four such rods extending into bores of the housing 54 at the lower surface thereof and fixed to the housing 54 by said screws 80, respectively. The base plate 24 which forms the top wall of the housing 26 is itself formed with a plurality of openings 82 through which the rods 78 extend. It is particularly to be noted that these openings 82 are of a diameter larger than the rods 78 and that these rods 78 respectively extend downwardly through the openings 82 with clearance so that there is no slidable or other frictional engagement between the rods 78 and the wall 24, thus inhibiting the transmission of any vibrations to the structure through the rods 78. Within the housing 26 the lower ends of the rods 78 are fixed to a plate 84- which is in turn fixed to a displacing structure which may take the form, for example, of a fluid-pressure device 86. This device may be either pneumatically or hydraulically operated, and actuation of the switch 34 will, for example, introduce air under pressure from a compressed air tank into the cylinder of the device 86 so as to displace the piston therein, or a hydraulic structure may be provided for this purpose, if desired. Also, it is possible to provide a structure where a threaded spindle passes through a rotary nut which is turned so as to displace the spindle which is connected at its top end to the plate 84 so as to displace the latter vertically. Any of these known displacing devices can form part of the moving means 76 for displacing the rnuffle means 52.

It will be noted that with this construction the muffle means and the support means both have a common vertical axis, and while the support means remain perfectly stationary the muflle means is displaced along this common axis between the lower operating position thereof shown in FIG. 2 and the upper inoperative position thereof shown in FIG. 1.

Because of the above-described structure of the invention, the work 12 will remain absolutely stationary not only during the treatment thereof in the heating chamber 58 of the muflle means but also during transition between its condition at the exterior of this chamber, shown in FIG. 1, and its condition in the interior of the chamber, shown in FIG. 2. In this way, any possible damage to the work resulting from vibratory movements are completely eliminated, and it will be noted that this result also is achieved in part by extending of the rods 78 with clearance through the openings 82.

At the same time, the structure is simple and compact and through the expedient of displacing the heating chamber 58 with respect to the work the latter is protected against any possible damage to an extent which is far greater than has heretofore been possible.

What is claimed is:

1. In a furnace for treating ceramic materials, stationary support means having an upper surface for carrying the work which is to be treated, muflle means having an opening in the bottom thereof defining a heating chamber for the work, moving means substantially vertically coaxial with said mufile means and operatively connected to the bottom portion thereof for displacing said muffle means from a rest position situated at an elevation higher than said support means and the work carried thereby to an operating position enclosing the work and at least a part of said support means.

2. The combination of claim 1 and wherein at least part of a structure for heating said muflle means is operatively connected thereto for movement therewith and has a flexible connecting structure extending from said muflle means.

3. The combination of claim 1, and wherein said muffle means is of a generally cylindrical configuration and includes an outer housing and an inner metal body carried by said housing in the interior thereof and having an opening therein to thereby form the heating chamber for the work.

4. The combination of claim 1 and wherein said support means includes a base plate and a pedestal assembly fixed to and extending upwardly from said base plate and having said upper surface for carrying the work, and wherein a vacuum tube communicates through said pedestal of said support means with the interior of said heating chamber when said muflie means is in said operating position thereof to be connected to a source of vacuum for evacuating the interior of said heating chamber.

5. In a furnace for treating ceramic materials, stationary support means for carrying the work which is to be treated, muflle means defining a heating chamber for the work, moving means substantially vertically coaxial with said mufl le means and operatively connected thereto for displacing said muflle means from a rest position situated at an elevation higher than said support means and the work carried thereby to an operating position enclosing the work and at least a part of said support means, said support means including a base plate and a pedestal assembly fixed to and extending upwardly from said base plate and having a top surface which forms said surface of said support means which carries the work, said base plate being formed with a plurality of openings situated beyond said pedestal assembly, and said moving means including a plurality of rods fixed to said mufile means and extending downwardly from the latter through said openings of said base plate, respectively, to an elevation lower than said base plate, so that vertical displacement of said rods through said openings of said base plate will result in displacement of said mufiie means between said rest and operative positions thereof.

6. The combination of claim 5 and wherein said moving means includes beneath said base plate a structure operatively connected to said rods for vertically displacing the latter.

7. The combination of claim 6 and wherein said structure of said moving means which is operatively connected to said rods is a fluid-pressure assembly which is fixed to said rods for displacing the latter vertically.

8. The combination of claim 5 and wherein a housing for a plurality of control instruments has a top wall which forms said base plate.

9. The combination of claim 5 and wherein said openings of said base plate are larger than said rods with said rods extending with clearance through said openings so that said rods remain out of engagement with said base plate during movement with respect thereto.

References Cited UNITED STATES PATENTS Pfanstiehl 13--3l Vaughan 263-40 Casey 26342 Hintenberger l3--22 X Negley 26340 Delange et al. 219-390 X Heim 13-31 X JOHN J. CAMBY, Primary Examiner 

